This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol3", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Puberulent or scabrous herbs, with thick opposite leaves, or the upper alternate, and small nodding, axillary and solitary, spicate racemose or paniculate heads of greenish flowers. Involucre hemispheric or cup-shaped, its bracts few, rounded. Receptacle chaffy, the linear or spatulate chaff enveloping the flowers. Marginal flowers 1-6, pistillate, fertile, their corollas short, tubular or none. Disk-flowers perfect, sterile, their corollas funnelform, 5-lobed, their styles undivided, dilated at the apex. Anthers entire at the base, yellow, scarcely coherent with each other, tipped with mucronate appendages. Achenes compressed, obovoid, glabrous. Pappus none. [Named after Ajuga Iva, from its similar smell.]
About 15 species, natives of America. Besides the following, 7 others occur in the southern and western United States. Type species: Iva annua L.
Heads spicate or racemose, each subtended by a linear or oblong leaf. Heads solitary, pedicelled.
Bracts of the involucre 4-5; heads 11/2"-2" high. Leaves serrate, oval or oblong; eastern.
1. I. frutescens.
Leaves entire or nearly so, obovate or oblong; western.
2. /. axillaris.
Bracts of the involucre 6-9; heads 3"-4" high; southeastern.
3. I. imbricata.
Heads spicate-paniculate; leaves dentate.
4. I. ciliata.
Heads spicate-paniculate, not subtended by leaves.
5. I. xanthiifolia.
Iva frutescens L. Sp. Pl. 989. 1753.
Iva or aria Bartlett, Rhodora 8: 26. 1906.
Perennial, shrubby or herbaceous, somewhat fleshy; stem paniculately branched above, minutely pubescent, or sometimes glabrous below, 3°-12° high. Leaves oval, oblong, or oblong-lanceolate, all the lower ones opposite, short-petioled, 3-nerved, acute or obtusish, serrate, narrowed at the base, the lower 4'-6' long, 1'-2' wide, the upper smaller and narrower, passing gradually into those of the racemose inflorescence which are much longer than the short-pedicelled heads; involucre depressed-hemispheric, its bracts about 5, orbicular-obovate, separate; fertile flowers about 5, their corollas tubular.
Along salt marshes and on muddy sea-shores, Massachusetts to Florida and Texas, the northern plant (I. oraria) mainly broader-leaved and less shrubby than the southern. Jesuits'- or false Jesuits'-bark. July-Sept.
Iva axillaris Pursh, Fl. Am. Sept. 743. 1814.
Perennial by woody roots; stems herbaceous, ascending, glabrous or sparingly pubescent, simple or branched, 1°-2° high. Leaves sessile, entire or very nearly so, obtuse, faintly 3-nerved, obovate, oblong, or linear-oblong, 1/2'-1 1/2' long, thick, somewhat fleshy, glabrous or pubescent, the lower opposite, the upper alternate and smaller, passing gradually into those of the inflorescence; heads mostly solitary in the axils of the leaves, 2"-3" broad, short-peduncled; involucre hemispheric, about 1 1/2" high; its bracts about 5, connate at the base, or united nearly to the summit; pistillate flowers 4 or 5, their corollas tubular.
In saline or alkaline soil, Manitoba and North Dakota to western Nebraska, New Mexico, British Columbia and California. May-Sept.